Method of making tension grid



Aug. 17, 1965 E. WENZEL ETAL 3,200,855

METHOD OF MAKING TENSION GRID Filed April 25. 1961 INVENTORS EhrhcrdWenzel 8| Giin er Morquordt av 9A ATTW United States Patent 6 Claims.oi. 140-715 The present invention relates generally to the production oftension grids for electric discharge tubes, and more particularly to aprocess and mechanism for fastening the ends of the coiling wire to thetension frame which includes two struts and two transverse members, eachconnecting the struts at two opposed positions.

With the increasing diminution in size of electrode constructions, therehas been a changeover to tension grid technology in the production ofgrids because the small distances required between the individualelectrodes could no longer be maintained when using coiling grids of thetype which had formerly been in general use. These distances, especiallythe grid to cathode spacing must be kept extraordinarily small in orderto make it possible to operate the tubes in the desired upper frequencyranges.

In the production of such grids, frames are generally used whichcomprise two struts or rods and four transverse members connecting thesetwo struts with one another. .Both the struts and the transverse membersare usually made of molybdenum.

According to this method grids are produced today wherein the strutshave a diameter of 0.8 mm. and the coiling wire of the grid has adiameter of 0.008 mm. The grid wire is put onto these frames with atension corre sponding to about '70 to 80 percent of the tear strengthof tungsten.

In order to make sure that the grid surface proper, which is enclosed bythe two transverse members, is entirely filled with grid windings, thecoiling process ordinarily starts about five to six windings before andends about two to six windings after the coiling space proper has beencovered or filled with windings.

After finishing this coiling process, the windings and the ends of thecoiling wire are fixed with glass paste and subsequently annealed atabout 800 C. After such a grid has been finished, the additionalwindings placed onto the ends of the grid frame, must then be unwound sothat actually only the portion of the grid frame between the transversemembers is covered with grid windings. This unwinding of the ends of thegrid wire, however, is an extraordinarily difficult operation whenusing, for eX ample, a tungsten wire having a thickness of 0.008 mm.Such a grid coiling wire cannot be seen with the naked eye and thecoiling operator must therefore carry out the removal of the coilingwire ends under an eyepiece.

There have also been known further methods for fastening the ends of thegrid windings. In one of these known constructions the first and lastwindings of the coiled grid wire are fixed together with a transversemember on a longitudinal strut by spot welding or spot soldering. Theend of the coiling wire and the tension frame may also be fused togetherwith the addition of metallic powder.

It is furthermore known to fasten these coiling wire ends to a metalpiece by clamping and to weld this metal piece, in turn, to the gridframe.

Finally, it is known, according to a further method, to carry thecoiling wire end of one grid and the beginning of the coiling wire ofthe following grid around the respective ends of the transverse membersand along the same longitudinal strut. In this known method, theintermediate piece of the grid wire is fastened by means of a metal bandwelded onto the intermediate piece of the strut, which metal band clampsthe intermediate piece of the grid wire.

As far as welding processes are concerned, there is a danger ofcombustion with the comparatively thin grid wire. The other knownmethods appear quite complicated, thereby raising the costs ofmanufacturing the grids.

An object of the present invention is to simplify the manufacture ofsuch grids.

Another object of the invention is to provide a tension grid which maybe manufactured without welding the thin grid wire.

A further object of the invention is to provide a method, article andapparatus which are simple yet exceedingly effective for the purposesfor which they have been designed.

These objects and others ancillary thereto are accomplished according topreferred embodiments of the invention the method of which comprisesplacing the end of the coiling wire between one leg of a transversemember and the respective strut before the start of the coiling process,and subsequently bending the free leg of the transverse member onto thestrut to clamp the end of the coiling wire. As is known, the transversemembers are connected with the struts by welding. In the processaccording to the invention, there are irregularities present on thesurface of the welding breast between the transverse member and thestruts, and the coiling wire when pressed onto this surface conforms tothese irregularities and is thus drawn around many small corners whichprevents the coiling wire from being pulled out.

Due to the clamping of the coiling wire ends between the struts and theoverlying portions of the transverse members, the pasting and annealingoperations are eliminated, thus resulting in a considerablesimplification of the manufacturing process.

For the automatic operation of the coiling process, it is only necessaryto carry the guide of the grid coiling machine in such a way as to makea movement enabling the clamping of the coiling wire end before thebeginning of each coiling process. After the end of the coiling wire hasbeen put in, the free legs of the transverse members are pressed againstthe grid strut by means of two pressure pins arranged at the gridcoiling machine. For this purpose it is necessary for the free ends ofthe trans verse members to project far enough to enclose, from thecenter of the strut, about one fourth of the circumference of the strut.I

Additional objects and advantages of the present invention will becomeapparent upon consideration of the following description when taken inconjunction with the accompanying drawings in which:

FIGURE 1 is a fragmentary elevation of a part of a tension grid producedby the process of the invention.

FIGURE 2 is a side elevation of the grid during an initial step in theprocess.

FIGURE 3 is a side elevation similar to FIGURE 2 illustrating the pins 6and the final position of the ends of the transverse members, in dottedlines.

FIGURE 4 is a side elevation of the finished grid.

The two spars or struts of the grid are designated as 1 and 2 and thetransverse members are designated as 3 which are connected at welds 9.Before the beginning of the coiling process, end 5 of the grid coilingwire 4 is placed between one leg of the transverse member 3 and thestrut 1. By means of a tool shown in FIGURE 3, consisting of two pins 6,the ends of the transverse members are subsequently bent in thedirection of the strut 1 in such manner as to clamp end 5 of the coilingwire. For this purpose, the two pressure pins 6 move in the direction ofthe two arrows shown. The front edges of the two pressure pins are sodesigned as to bend oif the ends of the transverse members in such a wayas to cause them to closely engage the arcuate surface of the strut 1.This position of the ends of the transverse members is shown in FIGURE 3by dashed lines and designated as 7.

The movement of pins 6 may be accomplished in any desired manner. Forexample, pin guiding blocks'13 may be mounted near or on the gridcoiling machine. The blocks have guide openings 10 formed therethroughin which pressure pins 6 are slidably movable. The piston rods 11 ofhydraulic cylinders 12 are connected to pins 6 and when the cylindersare actuated to extend their piston rods the pins 6 are moved towardeach other while when their piston rods are retracted, the pins 6 aremoved away from each other.

FIGURE 4 shows a completely coiled grid viewed from the front side. Theclamp wire end may be seen from this figure.

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes, andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

What is claimed is:

1. In the production of tension grids for electric discharge tubes, amethod of fastening the ends of the coiling wire to the tension frameincluding two struts and two transverse members each connecting thestruts at two opposed locations, the improvement comprising the stepsof: placing the end of the coiling wire between one leg of a transversemember and the respective strut prior to initiating the coiling process;and subsequently bending the free legof the transverse member onto thestrut to clamp the end of the coiling wire.

2. In a grid coiling machine for clamping a coiling wire to a tensionframe including a strut and two transverse members having projectingportions, an assembly for clamping the coiling wire between the strutand one of said transverse members, a guide cooperable with saidassembly and mountable on the machine for movement making possible theclamping of the end of the coiling wire before the beginning of eachcoiling cycle.

3. The device or" claim 2, wherein said assembly includes two pressurepins for pressing the projecting portions of the transverse memberstoward the strut after the coiling wire has been placed between thestrut and one of said projecting portions.

4. A method of clamping a coiling wire to a tension frame having a strutand two transverse members connected at opposed points to the strut andhaving projecting portions, comprising the steps: placing an end of thecoiling wire between the projecting portion of a transverse member andthe strut, and then bending the projecting portions of the transversemembers against the strut to clamp the coiling wire therebetween.

5. The method of claim 4, wherein said steps are performed prior toinitiating coiling of the wire onto the,

frame. a

6. Means for retaining the coiling wire of a tension grid for electricdischarge tubes in place, comprising, in combination: a strut; twotransverse members connected thereto at opposed points and havingportions projecting beyond said strut; two pressure pins in alignmentwith the projecting portions of said transverse members with onedisposed on each side thereof; and meansfor moving said pins toward saidstrut to bend the projecting portions against the strut to clamp acoiling wire therebetween.

References Cited by the Examiner UNITED STATES PATENTS 2,853,104 9/58Johnson l407l.5 2,960,621 11/60 Lane et al 313- 350 3,001,555 9/61 Meale7l.5 3,013,176 12/61 Field 3l3350 3,054,430 9/62 Van Tol et a1. 1407l.53,081,800 3/63 Crosby ct al. 140-7l.5

CHARLES W. LANHAM, Primary Examiner. RALPH G. NILSON, Examiner,

2. IN A GRID COILING MACHINE FOR CLAMPING A COILING WIRE TO A TENNSIONNFRAME INCLUDING ASTRUT AND TWO TRANSVERSE MEMBERS HAVING PROJECTINGPORTIONS, AN ASSEMBLY FOR CLAMPING THE COILING WIRE BETWEEN THE STRUTAND ONE OF SAID TRANSVERSE MEMBERS, A GUIDE COOPERABLE WITH SAIDASSEMBLY AND MOUNTABLE ON THE MACHINE FOR MOVEMENT MAKING POSSIBLE THECLAMPING OF THE END OF THE COILING WIRE BEFORE THE BEGINING OF EACHCOILING CYCLE.